title: Alpha-synuclein overexpression increases phospho-protein phosphatase 2A levels via formation of calmodulin/Src complex.
abstract: Alpha-synuclein (α-Syn) is the principal protein component of Lewy bodies, a pathological hallmark of Parkinson's disease (PD). This protein may regulate protein phosphatase 2A (PP2A) activity, although the molecular mechanisms for α-Syn-mediated regulation of PP2A and the potential neuroprotective actions of PP2A against PD-associated pathology remain largely unexplored. We found that α-Syn gene overexpression in SK-N-SH cells and primary neurons led to PP2A/C phosphorylation at Y307, a known target of Src kinase, and consequent phosphatase inhibition. In addition, phospho-activated Src (p-Y416 Src, pSrc) was higher in SK-N-SH cells and primary neurons overexpressing α-Syn. Thus, α-Syn may promote Src activation and PP2A inactivation, leading to hyperphosphorylation of proteins. Immunoprecipitation revealed higher calmodulin/Src complex formation in α-Syn-overexpressing cells and α-Syn transgenic mice. A TUNEL apoptosis assay and an MTT cell viability assay demonstrated that the PP2A activator C2-ceramide protected neurons against α-Syn-induced cell injury. Buffering the Ca(2+) elevations induced by α-Syn overexpression ameliorated the cytotoxicity of α-Syn. Our findings define a potential molecular mechanism for α-Syn-mediated regulation of PP2A through formation of the calmodulin/Src complex, activation of Src, and Src-mediated phospho-inhibition of PP2A. Overexpression of α-Syn may lead to neurodegeneration in PD in part by suppressing the endogenous neuroprotective activity of PP2A.
authors.affiliation: Beijing Institute of Brain Disorders, Capital Medical University, Key Laboratory for Neurodegenerative Disease of the Ministry of Education, Beijing Center of Neural Regeneration and Repair, Beijing 100069, China.
authors.forename: W
authors.initials: W
authors.lastname: Yang
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: C
authors.initials: C
authors.lastname: Duan
authors.forename: L
authors.initials: L
authors.lastname: Lu
authors.forename: H
authors.initials: H
authors.lastname: Yang
mesh_terms: D000818:Animals; D001483:Base Sequence; D002147:Calmodulin / Q000096:biosynthesis*; D045744:Cell Line, Tumor; D017931:DNA Primers; D006801:Humans; D020287:In Situ Nick-End Labeling; D051379:Mice; D008822:Mice, Transgenic; D010766:Phosphorylation; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D051844:alpha-Synuclein / Q000378:metabolism*; D019061:src-Family Kinases / Q000096:biosynthesis*
chemical_list: D002147:Calmodulin; D017931:DNA Primers; D051844:alpha-Synuclein; D019061:src-Family Kinases; D054648:Protein Phosphatase 2
keywords: Alpha-synuclein (α-Syn); Parkinson’s disease (PD); Protein phosphatase 2A (PP2A); Src kinase